Twitter can now censor tweets by country

Twitter said Thursday that it now has the ability to “reactively” block tweets so they won’t be seen within a specific country, although the San Francisco company vowed that “the tweets must continue to flow.”

Twitter announced the change one day after the one-year anniversary of the start of the revolution that toppled the regime of former Egyptian President Hosni Mubarak. That Arab Spring uprising, along with the Occupy Wall Street movement in the U.S., gained popular support with messages spread through online mediums like Twitter, Facebook and YouTube.

The change could set Twitter up for criticism that it will censor the free speech rights of users. But it could also open a window for Twitter to enter huge markets such as China, where censors have blocked the service since 2009, shortly before the 20th anniversary of the Tiananmen Square democracy protests.

In a company blog, Twitter said the growing microblogging service is in or plans to enter countries “that have different ideas about the contours of freedom of expression. Some differ so much from our ideas that we will not be able to exist there. Others are similar but, for historical or cultural reasons, restrict certain types of content, such as France or Germany, which ban pro-Nazi content.”

Until today, Twitter could only block tweets – for reasons such as to curtail spam or because they violate the terms of service or copyright laws – completely for everybody, but not by country.

So starting immediately, Twitter said, “We give ourselves the ability to reactively withhold content from users in a specific country – while keeping it available in the rest of the world.”

When Twitter does block a tweet, it will replace it with a message that reads “Tweet withheld” or saying that the user name has been withheld. While residents within the country would see that message, the rest of the world would still see the original tweet.

There will also be a link to find out why on a site run by ChillingEffects.org, a joint project of the Electronic Frontier Foundation and the Harvard, Stanford, Berkeley, University of San Francisco, University of Maine, George Washington School of Law, and Santa Clara University School of Law clinics.

The account holder then has a chance to contest the block, or delete the account.

“We hold freedom of expression in high esteem and work hard not to remove tweets,” Twitter spokeswoman Jodi Olson said in an e-mail. “The key is that this reactive only. It’s on a case-by-case basis, in response to a valid request from an authorized entity. And just to be clear, this is not a change in philosophy and there are still countries to which we will not go.”

The Twitter blog entry noted the company has not yet used the country-specific block, but if required, “we will attempt to let the user know, and we will clearly mark when the content has been withheld. One of our core values as a company is to defend and respect each user’s voice. We try to keep content up wherever and whenever we can and we will be transparent with users when we can’t. The tweets must continue to flow.”